Contact arc suppression



Ap 1952 P. M. G. TOULON CONTACT ARC SUPPRESSION 4 Sheets-Sheet 1 FiledJan. 14, 1949 April 1952 P. M. G. TOULON CONTACT ARC SUPPRESSION 4Sheets-Sheet 2 Filed Jan. 14, 1949 INVENTOR.

P!ERRE M. G. TOULON April 29, 1952 P. M. G. TOULON CONTACT ARCSUPPRESSION Filed Jan. 14, 1949 4 SheetS-Sheet 3 1 PIERRE M. G. TOULONApril 29, 1952 P. M. G. TOULON 2,595,024

CONTACT ARC SUPPRESSION Filed Jan. 14, 1949 4 Sheets-Sheet 4 INVENTOR.

PIERRE M G. TOULON Patented Apr. 29, 1952 CONTACT ARC SUPPRESSION PierreMarie Gabriel Touln, Paris, France, as signor to Products & LicensingCorporation, New York, N. Y., a corporation of Deiaware Application January 14, 1949, Serial No. 79,926 In France J anuary 19, 1948 1.!)Claims. 1

The present invention relates to a new method and apparatus for breakingelectrical circuits, which carry currents of a relatively high intensity, without the resultant emissicn of sparks or arcs.

The invention relates more particuiariy to the separation of contactsthrough which flows a strong current, without initiation of an arc, suchas usually coeurs between such contacts.

The invention is applicable more particularly to break switch systemsfor industrial currents at high voltage and current, as well as to allelectrical machines which present the problem of commutation, and inwhich the invention would permit the suppression of sparks resultingtherefrom.

According to the general concept of the invention, a rectifier isinserted in series with the break switch in the first case, or with thecommutation brush in the second case; and previous to the break, or tothe commutation, an auxiliary voltage is introduced into the circuit(voltage which will be designated in the text as countervoltage), and inthe opposite direction to the one which causes the current, and of anamplitude which would only need to be at least equal to it, but whichmay be greater.

The combined actions of the counter-vcltage and of the rectifier havethe effect of bringing about a progressive reduction of the current tozero, which operation permits the separation of the contacts without anysparks; because of the rectifier the counter-voltage, no matter what itsamplitude, can never reverse the current in the circuit and therebyprevent the desired result, since no current in the reverse directioncan be caused to fiow through the rectier. Of course, this rectifiermust be inserted into the circuit in such a way as not to obstruct theflow of normal load current.

This concept of using counter-voltage of any.

value whatsoever, permits one to generate this counter-vcltage by meansof a generator of relatively very simple design and which requires noprecise regulation, a gencrator which on the other hand rentiers theoperation very certain.

In case electromotive forces should appear in the circuit that one isseeking to open, resulting from variation in current in that circuit,one should give to the counter-voltage a minimum amplitude sufiicient tocompensate these electromotive forces, in addition to those which existnormally in the circuit. This situation occurs notably if the circuitoffers a certain self-induction, as in the case of commutation machines.The counter-voltage must be released in an excessively short time, andthis brings about the passage 01' very strong instantaneous currents.

In crder to obtain abruptly the very great powcr one needs at thedesired moment, the

invention provides a preferred means to introduce this counter-voltage,without requiring a mechanically controlled device. Specifically, Iemploy an are in air relay, based upon the use of two spark gaps, placedat a certain distance one from the other, with an electron controldevice situated in the vicinity. This relay requires only aninfinitesimal amount of energy to control a large current.

According to a variant of the invention, the current is reduced in thecircuit at the contacts which are to be separated, by making it passprogressively in a line shunted on this circuit:

in this case, the counter-vcltaga may be introduced either directly intothe first circuit, or into the shunt, in reversing the polarity.

In the case in which one applies the invention to a circuit breakerswitch, a variation of the invention consists of putting a rectifier inseries with the switch, and of branching in parallel to this circuit acondenser in series with a coil into which has been introduced thecountervoltage in question. The eiect of this latter is to switch thecurrent progressivcly from the switch towards the condenser, which isprogressivcly charged and the switch is opened when the current in thecontacts has completely stopped. The effect of this is that thecondenser continues to be charged, until it has balanced the voltage ofthe network. The condenser employed must be consequently capable ofhandling the total voltage of the network, and it must on the other handhave great enough capacity to be able to absorb suificient charge.

T0 recluce the size of this capacity, according to another variation ofthe invention, the operation of circuit opening may be executed in twosteps, by twice following the procedure to which the invention relates.Tvvo interrupters arranged in series one with the other are utilized. Thopening of the first interrupter brings about a primary' reduction ofthe current, by inserting a resistance in series. Afterwards the secondinterrupter is opened, thereby completely opening the circuit, in thesame way as has been described in the variation mentioned above.

The arrangement consists therefore in introducing in series with theprincipal interrupter, an auxiliary circuit opening devise with a shuntin parallel,- which will have an appropriate resistance. In conformitywith the procedure already described, all of the current is divertedinto this shunt and the auxiliary interrupter is then opened. Aresistance is thereby inserted into the circuit, the efiect of which isto reduce the current to a-small fraction of its original value.

The principal interrupter then comas into use, and one succeeds incutting the current without producing sparks by diverting momentarilythe current into a condenser, in the manner already described above. Butthe current to be annulled being much weaker, the required size ofcondenser is notably reduced.

The invention is applicable also to cases in which the break is due toan accidental cause, for example, a short circuit. The inventionprovides in this case means, controlled by the abrupt increase incurrent, to introduce a circuit in shunt with a breaker switch, and to.SWitch the current into the latter, the resistance of the shuntpreventing the current from acquiring dangerous proportions.

According to a variation of the invention, in a case where it would beapplied to a rectifier or to the commutator of a D.C.-=A.C. rotarytrans-' former, each brush ordinarily used is replaced by two rotarybrushes which bear on the fixed segments, and which Will be coupled tothe secondary of a transformer laid out in so many rows; and in serieswith each brush is connected a rectifier and a coil into which a voltagemay be induced.

One applies alternately in the circuit of these brushes acounter-voltage for reclucing progressively the current of the brushes.This operation begins before the brush has left its segment; and thecounter-voltage is introduced by means of a source of voltage controlledby the rotation of the brush.

According to a prefzerred variation of the invention, this Voltage isapplied by means of a transformer whose secondary has its terminalsconnected to the brushes. The brushes are driven by a motor,synchronized With the frequency of the network. The shaft of this motordrives a small alternator which will furnish a frequency in synchronismwith that of the network. This Irequenoy is used to feed the primary ofthe auxiliary transformer.

The alternator may be either two-phase, in which case there is requiredonly two rows of brushes, or poly-phase, for example hexaphase, in whichcase the steps are arranged on six independent rows regularly shiftedwith respect to one another.

The drawirigs accompanying the text will help in understanding betterthe new method, to which the invention relates, together with the meansemployed for its execution.

Figure 1 illustrates an embodiment of the invention which employs arectifier and an auxil iary voltage, to suppress current fiow at themoment et circuit opening.

Figure 2 represents, as a function of time, the currents and voltages inthe diierent circuits of Fi ure 1.

Figure 3 illustrates a variant of the, system 01 Figure 1, in which twoparallel circuits are employecl.

Figure 4 is a circuit diagram of a system for breaking current at highvoltage, in accordance with the invention.

Figure 5 is a circuit diagram of a system for providing protectionagainst short-circuits, in electrical systems, in accordance With theinvention.

Figure 6 illustrates the application of the invention to a high tensioncommutator.

Figure 7 illustrates a perfected variant of the system of Figure 6,utilizing a polyphase commutation voltage.

Figure 8 illustrates on a greatly enl&rged scale, 2. portion of the r0Wsof brushes, showing et. ea ch 4 instant the relative position of thebrushes in relation to the commutator segments.

In referring to the accompanying drawings, l provide examples, which arenot limitative, of the invention in operation.

Figure 1 is a circuit diagram of a system which illustrates theprinciple of the new procedure to which the invention relates. W may bea source of either continuons current. or of. variable current, providedhowever that the frequency of this current be relatively small inrelationship to the speed of the phenomena occurring in the system. Thissource fiows into a circuit presenting a resistance N and an inductanceL. The problem that 1 propose to solve is that 01 interrupting thecurrent by means of an interrupter C (whose points 01 contact have beenrepresented by semicircles in the drawing) without any sparks beingproduced at the moment of the interruption.

In conformity With the invention, a rectifier R placed in series withthe circuit, oriented in such et direction that it 1ets the current flownormally, and a device U (generally the secondary of a transformer) isintrocluced in which one can momentarily cause to appear a tension X,thanks to an exterior device G (for example by throwing into the primaryof the transformer U a variable current).

Let us call i the current which circulates in the circuit, and E thevoltage betvveen one of the terminals of source W and a terminal of theinterrupter C.

According to the invention, the current which circulates in thecontactor C is annulled by generating, by means of the device G, avoltage U, which will be equal to or greater than E.

In Figure 2, the first curve, 2a, represents as a function of time, thevoltage U.

The curve, 2b, represents, in function of time, the voltage at theterminale of the rectifier R; the third curve, 2c, represents, as afunction ci time, the current 2; and the fourth curve, 2:1, representsas a function of time, the voltage be tWeen the electrodes of thecontacter C.

Let us suppose that one wishes to interrupt the current 2' at the timeT1, the generator G induces progressively in U a voltage, which, inconformity With the invention, exceecls the voltage E. In proportion asthe voltage U increases, the current i is reduced progressively. If thevoltage U is greater than W, the current 2' is annulled. At the time T2,beginning With this moment, the rectifier assumes a voltage of reversepolarity, as shown on curve 2b. Thanks to the pres ence of the rectifierR, the current romains zero from T2. At any time whatsoever, forexample, at the moment T3, one may separate the two points of contacts Cwithout any sparks being produced.

The voltage between the electrodes C, which is at first nul], increasesprogressively and attains finally, after a fairly long time, the value W(time T4). Meanwhile the voltage at the terminals of the rectifier,which was originally equal to Va at the moment of the cutting oi, cornesprogressivcly back to zero.

The instant of the cutting off, 'I3, may be set anywhere in the intervalXX, during which the voltage induced by G on U furnishes a voltagegreater than W.

In all cases, sepamtion of the contacts C does not cause any sparkresulting from the break, since, because of the rectifier B, the currentflowing in the circuit h as not been able to reverse itself, and sincethe current is consequently zero.

The invention solves therefore the problem of breaking current fiow,without sparks, the only condition being that the induced voltagegenerated in U be sufficiently high.

Figure 3 illustrates a variant of Figure 1, in which two circuits inparallel are employed. This system is particularly interesting when theinput voltage W is very high and when one is trying to break the circuitwithout using too high tensions U.

We find again in this figure, the supply voltage W, the resistance N,the inductance L, in which circulates the current X 2, but instead ofonly one circuit, I utilize two parallel branches, a first branch, U1,R, C, traversed by the current il, and a second branch U2, traversed bythe current i2. We designate as above, by E the voltage across U1+R+C.According to this second variant, the generator G can induce either avoltage U1 et the opposite sign to E, in one of the parts branches ofthe circuit or a voltage U1, of the saine sign as E, in the otherbranch.

In conformity with the invention the voltage provided by generator G hasthe eifect of annulling the current 7:1, and of thereby permitting theseparation of the contacts C without sparks or arcs resulting from thebreak.

Figure 4 illustrates in detail a system corresponding with the systemsschematically illustrated in Figure 3, as applied to the interruption ofa high voltage circuit.

Let us suppose that the source W feeds a circuit l including aninductance 3, and a resistance 2; and in conformity with the invention,a

rectifier 4, in series With contacts 5, both in parallel with a winding6 and the resistance 1. Let, us call E1 the tension et the terminals ofthese two circuits in parallel With each other, and in series with thelatter a rectifier [2 and contacts l3, with a circuit in parallel Withthe latter comprising a.transformer 14 and a condenser I5, and let E2 bethe voltage across the latter parallel circuit.

To induce in the transformer 6 a transient voltage in Figure 4, I employa source of continuous current Il, feeding, across a high resistance l0,a condenser 9. The discharge of thecondenser 9 can, in the primary coilof transformer 6, be obtained at the moment desired, thanks to theswitch 8.

T induce in the coil l4 a transient voltage, I employ a source Il,feeding, across a high resistance Il, a condenser 16. The discharge ofthe condenser l6 in the primary winding of the transformer [4, may beinitiated at the moment desired, by means of the device F2 contained inthe block 8l. This device comprises two electrodes l8 and [9, betweenwhich an arc may arise, and an electrod 20 placed in the vicinity ofthese two electrodes, and the potential of which controls release of thearc. This potentia1 of the electrode 20 is modified by utilising a smallauxiliary source 2l, a resistance, and a small auxiliary switch 22.

Let us examine first the operation of the first system of breakingcontacts 5. In conformity with Figure 3, one succeeds in discharging inthe parallel branch 61, all of the current 2', which, until then, couldcirculate in the two branches in parallel at the same time.

The opening of the contacts has. the effect of inserting in theprincipal circuit et resistance, which in turn has the eifect ofreducing consid- 6 erably the current I. The operation of this systemhas already been described in connection with Figure 3.

Let us consider now the operation of the second system of openingcontacts [3. On account of the capacity 15, which is progressivelycharged, there is induced in condenser 16 a voltage equalinstantaneously to the voltage E2. Beginning with this moment, it ispossible to open the contacts [3, because if the fiow of the current 72is totally utilized to assure the charging of the condenser l5, and ifno current circulates in the contacts l3, but, to the contrary of thepreceding case, the current i can now arinul itself, because, after acertain time, the charging current of the condenser l5 terminates andthe total voltage W appears at the terminals of the condenser.

The two step operatioh above described is of great interest, because thecondenser must have a capacity large enough to take a charging currentas great as the current which is to be interrupted. In the case wherethe current is great, one is led to employ very great capacities.

The voltage at the terminals of these condensers corresponds finally tothe voltage W, it is necessary that the break clown voltage of thcondenser be very high; it follows that the price of these condensers isvery high.

In reducing at first, by means of the resistance 1, the current 2' to afraction only of its original value, one reduces the necessary capacityto the same extent. Instead of a single pair et contacts 5 and a singleresistance 1, one can very well, evidently, place several of them inseries, and one Will reduce then successively the current, for example:to /3, to ,6, to /27, etc. of its value. The same rectifier 4 and thesame coil 6, can successively be utilized to carry out these successiveinsertions by employing a suitable switch.

In a case where the system must b used as break switch, the closing ofthe switch 8 (or 3),

which assures the discharge of the condenser 9 (01' IS), must be veryrapid and it is necessary that this switch, which permits a very stronginstantaneous current to pass, be controlled by a minimum current. Therelay spark gap shown in the block *8 is therefore of great interest,because it has no movable parts and it can operate in an extremely shorttime, and is not slowed by the mechanical inertia cf parts. Itsoperation is based upon the observation of the following physicalphenomenon: if a ring 20 is installed in the vicinity of two electrodes,for example, two bars of tungsten, between which a r'ather strongdiflerence in continuous potential, one observes that for a certaindistance of the electrodes a spark shoots forth or on the contrarv doesnot shoot forth, according to the potential of the electrode 20 inrelationship to one of them, for example, the electrode l9. If thevoltage cf the ring is of the same sign as that of electrode I3, thespark has a tendency to prime itself much sooner and for a much lessgreat distance of the electrode than if the tension is of the oppositesign. A variation in voltage of a few hundred volts applied to theelectrode 20, is thus sufiicient (for a judicious distance of theprinicpal elec trodes I8 and l9), to enable flow of th current.

Figure 5 is a variation of Figure 4,'more ecpecially adapted toprotection against short circuits. Crie finals again on this diagram thesame principal elements (source W, load 2, contacts [3, rectifier l2;and a coii I in which is induced the voltage U, etc.)

The short circuit of the line is represented in the Iorm of switch 25,When this short circuit 15 produced, the generator W has a tendency togive out a much stronger current than th normal one. But, thanks to theself-induction 3 of the generator and of the line, this currentincreases progressively and relatively slowly.

In conformity with the invention one utilizes this increase to open thecontacts l3, which inserts very rapidly into the circuit a resistance24, having the eifect cf limiting the augmentation of the current to anadmissible value. In conformity with the invention, one installs inseries with this resistance 24, a coil I, in which a variation ofcurrent flow is provoked, which has the efiect of balancing completelythe current which was fiowing until then. There is shown at 12, aspreviously, the rectifier which prevents the current from reversingitself in the contacts [3.

There is shown, at 28, in the form of a relay, the element Whichcontrols the intensity, either for the absolute value appropriately highof the current, or for the eifect of its rapid increase. There is shown,at 2", the coil of the mechanism 26 which eects separation of thecontacts [3.

Th relay 28 closes the switches 29 and 30. The switch 30 has the effectof closing the circuit of the first transformer I4, the current in whichannuls momentaneously the current in the contacts I3. I utilize thedischarge of a condenser H5, maintained at high voltage by a source Il,through a resistance Il. The switch 29 closes the circuit of anauxiliary battery 31 and applies current to the C011 2! which actuatesthe mechanism 26, for opening contacts 13. Because of the self-inductionof the coil 28 (and of the inertia of the mechanism 25) the separationof the contacts l3 is produced noticeably at the moment when thevariation of current flow (due to the discharge current of the condenserl6) attains its maximum, that is to say at the moment when th voltage inthe secondary M passes through its maximum. The resistance 24 is chosento have a value comparable to that of the resistance 2, in such a waythat, in case of a short circuit, the current after having momentarilyexceeded slightly the normal value corne progressively back to it aitera fairly short time. Of course, one can join to this system ofprotection against short circuits and excessive voltage anormal systemof breaking the current ,such as is described in Figure a, this latterhaving the purpose of limiting t a very short time interval the durationof the passage of the current in the resistance 24 (Which must as amatter of fact, collect a considerable quantity of calories per second)This last group is then released automatically, immediately iter theputting into service of the first.

Figure 6 shows the application of the system of Figure 3 to a system ofrectification cf alternating triphase current into a continuous current.

The triphase feeding current is supposed to excite a coil winding 31, inthe form of a ring gramme immovable in space. Rotary brushes driven by alittle synchronous motor Will rub against this ring.

In order not to complicate the dravving unnecessarily, the wires of theprimary power sources have not been shown, and the ring 8 nectedrespectively to the segments 34 and to the segments 35, arrangedalternately on two coaxial rows.

On these rows run respectively the rotary brushes 32 and 33. In serieswith the brush 32 is a rectifier R1; and in series With the brush 33 isa rectifier R2. The other terminals of the rectifiers R1 and R2 areconnected respectively to the terminals of a group of two secondarycoils SI and S2. The junction of these two coils, ar ranged in series,are bound to the load W.

The brushes 32 and 33 are supposed to turn at the speed of synchronism,by a mechanism which is not shown and which comprises a synchronousmotor driven by a shaft coupled to the brushes.

This mechanism drives also a group of symmetrical brushes, not shown. Tosimpliy the diagram, only one brush 40 has been shown at the bottom ofthe drawing, in order to make clear how the circuit is closed, but itmust be admitted evidently that the disposition of the circuits in thelower part of the drawing, is exactly analogous to that described above.

The arrangement comprising a single group of brushes (such as d) runningin synchronism, is well known in the art.

The use of a single positive and a single negative brush, such as 49,causes, as is known, a difiicult commutation problem.

The procedure of the invention, which makes freedom from arcs and sparkspossible, solves this problem completely.

As a matter of tact, the two brushes 32 and 33 utilized in conjunctionWith the coils S1 and S2 (in which one induces an appropriate voltage)and associated with the rectifiers R1 and R2, assure, as a matter offact, a perfect commutation, even for Very great voltages.

To create the appropriate voltage necessary to efiect sparklesscommutation, one feeds the primary P by means of an alternator G, whosefre quency corresponds to half of the frequency of commutation, that isto say, to the product of the number of steps of the segments 34 (or ofthe segments 35) by the frequency of the feeding network of the ringgramme. The voltage generated in the secondary windings Si and S2, hasthe eifect of annulling alternately the current of the brushes 32 and33.

I arrange the steps (or sections) in relationship to the brushes, insuch a way the brush gives forth no current from the moment when it isgoing to leave the section and that this current is only produced afterit rests in full on the following section.

While one of the brushes, such as 32 is discharged, the other, such as33, receives all the current given forth by the circuit or vice versa.

There has been previously mentioned the selfinductance and theresistance of the circuit, as has been already represented by R and L.This self-inductance L can be considerable without any inconvenience,being given that the current is never interrupted, but is only carriedintegrally alternatively from one brush to the other. One profits by themoment when each brush is discharged, to connect it from one step to thefollowing and this commutation is effectuated without any arc.

The turns in course of Commutation are designated on the drawing by .36.Being given that these turns present a certain self-inductance thecommutation is not instantaneous, and it is necessary to provide forthis a rather large period cf overlapping of the sectors in order toleave enough time for the current, which was fiowing by one of thebrushes, to be entirely carried over on the other. This time is so muchthe greater as the current is itself higher, that is to say, the machineis charged more and one is obliged to foresee very large sectors, whichfact renders the isolation between these sectors difficult.

In the examples mentioned with the figures, I have presented the case of2. machine rectifying a current and giving a voltage of given polarity,but it is evident that in changing the direction of the rectifiers R}.and R2, the appliance may be used in the reverse way, that is to say, asa wave generator, on the condition that voltages of appropriate phasesare induced on the coils S1 and S2.

Figure 7 illustrates a variant of the system of Figure 6, but instead ofusing an arrangement, in form of a ring, I use simple monophasetransformers, appropriately connected. The system is applicable also tothe case of a rectifier permitting the transformation of the energy of atriphase source il to a source of continuons currnt at high voltage 68.I multiply the number of phases of the triphase distribution by means ofa number of static transformers. In Figure 7, use is made of 12monophase transformers, the primaries of which are connected in atriangle, 4.2, and in a star, 43, and the secondary windings 44, 45,4&6, 41, 48, 49, 511, 5l, 52, 53, 54, 55, of which were connected inseries, in such a way as to constitute a polygon with 12 sides(resembling a ring gramme). Suppose that on each of the secondaries ofeach transformer are 5 equidistant contacts which are connectedalternately to the sectors il, I2, I3, 14, I5, "5, alranged in fixedindependent rows. On these rows suppose that two groups of brushes I1,18, le, 853, 8l, 82, and H, I8, I9, 8D, 81, 32, are disposed at 180 onefrom the other. T0 simplify the drawing, one has not shown junctionrings between the fixed and rotating parts. These brushes are fixed acommon rotating frame 60 driven at the speed of synchronism, by means ofa small synchronous motor 64, fed by the sector 4l.

in conformity With the invention, I install on the axis of the motor 64,a little alternator, 63, of commutation without sparks, in conformityWith the new patened procedure. The receptacles are connectedalternately to 6 independent rows il,l2,l3,l4, 15,16. The steps of theserows are shifteol one in relation to the other by of the distance whichseparates the axes of two successive sectors.

In conformity with the invention, I install on the axis of the motor 64,an alternator 63 furnishing a triphase voltage 84, the frequency of thisalternator being equal to the product of the number of steps situated oneach row by the number of rotations per second efiectuated by the frame60. With the assistance of the power source 84, I feed the primaries 85and 85 of the two polyphased transformers. The secondaries 86 and 86 areconnected each in a 6 branched star, the neutral points of these starsconnected to the terminals of the load. Each of the phases of each ofthe secondaries feeds a rotary brush, across arectifier, such as 81 and81. The direction of this rectifier is established in such a fashionthat the current can only circulate in it in the desired direction ofthe feeding of the load 10 circuit 68, when the system is used to feedthis circuit with continuous current.

The rectifiers in liaison with the transformers 86, are sufiicient toassure sparkless commutation, as has already been described above. Thealternator 63 carries with it an excitation shunt field winding 86, butpreferably, it has also an excitation series field winding 61, so thatthe voltage induced in the transformers and 85' augments a great dealwith the charge, and this assures excellent commutation no matter whatthe charging regime: as a matter of tact, the voltage of self-inductioninduced in the windings during commutation increases with the charge,and it is therefore advisable to create an auxiliary commutationvoltage, to assure the commutation without sparks, proportionatelygreater as the charge is greater.

Figure 8 represents, on a large scale, and in their respectivepositions, the sectors of the different rows il, I2, 13, 74, 15, 16 onwhich the 6 brushes 11, I8, 19, 80, al, 82, contact.

In idle running or with a weak charge, the current begins to circulatein one brush (such as 11) as soon as the voltage of commutationfurnished to the brush surpasses that of the preceding brush and thebrush ceases to pass current /6 period after.

The current in the brush 11 only increases slowly and when theelectromotive force of selfinduction is equal to that of the voltage ofcommutation, one may observe in the intensity a level run. It is onlywhen the current attains in the following brushes, a notable currentthat the current is progressively reduced, and it only stops slowly. Thecommutation time is found to be considerably augmented, nevertheless,thanks to the new disposition, several brushes 2 or 3 for example, suchas I1, I8, I9, can give current forth simultaneously. Because of this,for a machine of a given power the current in each brush is considerablyreduced. Vice versa, for a given dimension of the brush, it is possibleto design a much more powerful machine.

On the other hand, the isolation between the successive steps may bemuch greater. As a matter of fact, as can be seen on Figure 8, there isrepresented at 88, the position of the brush in relationship to the step1]. There is shown on the other hand, at 89, the slope which permits thebrush to mount progressively on the following step, and where,consequently, the contact may be bad. It is only when the brush occupiesthe position Il, that the current can begin to circulate withoutdisadvantage in the brush. one may see, in Figure 8, in the mostdisadvantageous position that the remaining distance remainsconsiderable.

In the examples mentioned (for example, in the case of Fig. 6-) one hasonly represented a machine destined to transform alternating currentinto a continuous voltage of known polarity; but it is evident, that onecould obtain a polarity in the opposite direction by changing theshifting of the brushes on the synchronous motor at the same time asthat of the rectifiers R1 and R2; it is also evident that the appliancemay be used as an A.C. generator on condition that the direction of therectifiers R1 and R2 and the phases of the voltages induced in the coilsS1 and S2 are chosen appropriately. In a more general way still, one canadvantageously replace the rectifiers, each one by 2 thyratrons arrangedin inverse parallel, the grids of these thyratrons serving to blockalternately, at will, the working of one or the other of the littlerectifiers: one can thon with this appliance change, at will, thefrequency, the amplitudes of the currents and tensions, etc.

What I claim and desire to secure by Letters Patent of the United Statesis:

1. An electrical circuit interrupting system comprising a source ofvoltage, a load circuit, a pair of normally closed circuit making andbreaking contacts, a rectifier poled to pass current in response to saidvoltage, means connecting in series said source of voltage, said loadcircuit, said contacts and said rectifier, means for temporarilyimpressing in opposition to said voltage an auxiliary voltage at leastas great as said fi1st mentioned voltage, and means for thereaiteropening said contacts, whereby said contacts are opened during acondition of zero current flow in said load circuit.

2. A system for interrupting fiow of electric current in a high voltagecircuit, comprising, in combination: means for interrupting saidcircuit, means for generating a transient voltage having a polarityopposite to and in magnitude at least as great as said high voltage,means for impressing said transient voltage in said circuit, rectifiermeans connected in said circuit and poled to prevent reversal of Currentfiow in response to said transient voltage, and means for actuating saidmeans for interrupting during said transient voltage 3. A system inaccordance with claim 2 Wherein said transient voltage is connected inseries With said means for interrupcing.

e. A system in accordance with claim 2 wherein said transient voltage isconnected in parallel with said means for interrupting.

5. A system for interrupting the fiow of electrie current in a circuitat high voltage, comprising, in ccmbination: means for interrupting saidcircuit, means for generating a transient voltage, said last meanscomprising a condenser and a primary winding of a transformer connectedin series, a secondary winding coupled to said primary Winding, meansconnecting said secondary winding in said circuit, said transformerbeing adapted and arranged to induce into said secondary winding atransient voltage opposing said fiow of electric current in response todischarge of said condenser and of magnitude greater than said highvoltage, rectifier means connected in said circuit and poled to preventreversal of said electric current in response to said transient voltage,and means for actuating said means for interrupting during saidtransient voltage.

6. A system for interrupting fiow of electric current in a high voltagecircuit, comprising, in combination: first means for interrupting saidcircuit, second means for interrupting said circuit, said first andsecond means connected in series in said circuit, et resistive circuitshunting said first means for interrupting, means for reducingtransiently t zero voltage existing across said first means forinterrupting, means for actuating said first means for interrupting tointerrupting condition during said zero voltage, said electric currentthen fiowing to said second means for interruptin via said resistivecircuit, means for reducing current fiow in said circuit to zero for aninterval of time, and means operative during said interval of time foractuating 12 said second means for interrupting to interruptingcondition.

7. A system for interrupting fiow of electric current in a high voltagecircuit, ccmprising, rst means for interrupting circuit, a firstreetifier in series with said first means and poled to conduct saidcurrent in response said hign voltage, a resistance, an inductancc, inans connecting said resistance and inductance in series Wilh each otherand in shunt with said first means for interrupting and said firstrectifier, second means for interrupting circuit, a second rectifier inseries with said second means for interrupting and poled to conduct saidcurrent in response to said high voltage, a condenser, a secondinductance, means connecting said condenser and said second inductancein series with each other and in shunt to said second means forinterrupting and said second rectifier, means for inducing in said firstinductance a transient voltage adapted to reduce current fiow in saidfirst means for interrupting to zero and for actuating said first meansfor interrupting t0 interrupting condition during said transientvoltage, and means for thereafter inducing in said second inductance afurther transient voltage adapted to reduce currnt fiow in said secondmeans for interrupting to zero and for actuating said second means forinterrupting to interrupting condition during said further transientvoltage.

8. The combinaticn in accordance with claim 7 whercin each of said meansfor inducing comprises a condenser, a winding, means for charging saidcondenser to a predetermined potential, and means for rapidlydischarging said condenser into said winding to provide a rapid rate ofchange of current in said winding.

9. A commutator system, comprising, a ring transformer, a plurality ofpairs of ring segments, a pair of moving brushes each contactingsuccessive corresponding ones of said pairs of ring segments, meansconnecting predetermined points of said ring transformer topredetermiued ones of said ring segments, means for inducing alternatingcurrent in said ring transformer at irequency f, means for actuatingsaid brushes at a rotative velocity of f rotations per second, arectifier connected in series With each of said brushcs, a transformerhaving a primary winding and a secondary winding, means connecting saidsecondary winding between said rectifiers, and means for energizing saidprimary winding With current at frequency f.

10. A system in accordance With claim 9 wherein is further provided abrush making continuons contact with said ring transformer. means forrotating said last mentioned brush at frequency f, a load circuit, andmeans for connecting said load circuit between said last mentioned brushand a center point of said secondary winding.

PIERRE MARIE GABRIEL TOULON REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,188,361 Koppelmann Jan. 30,1940 2,195,818 Koppelmann et al. Apr. 2, 1940 2,293,296 Jonas Aug. 18,1942 2,301,752 Schulze Nov. 10, 1942 2,358,926 Hansen Sept. 26, 1944

